Series

The Y chromosome has been likened to a hall of mirrors because its sequence contains many sections that appear to be palindromes. These palindromes provide a clue to some interesting events that may have occurred during the course of the chromosome's evolution.

Meiosis, the form of cell division unique to egg and sperm production, sets the stage for sex determination by creating sperm that carry either an X or a Y sex chromosome. But what is it about the X or Y that determines sex?

How did the human Y chromosome become so small relative to its X counterpart? This animation depicts the 300-million-year odyssey of the sex chromosomes that began when the proto X and Y were an identical pair.